<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            font-size: 16px;
            font-family: serif;
            background-color: lightgrey;
            line-height: 50px;
        }

        span{
            font-size: 16px;
            font-family: serif;
            vertical-align: middle;
        }

        div.box{
            display: inline-block;
            background-color: lightcyan;
            height: 16px;
            width: 16px;
            vertical-align: text-bottom;
        }
        
    </style>
</head>
<body>
    <div>
        x<span>hello</span>
        <div class="box"></div>
    </div>
</body>
</html>